Nitrogen Powered Air Conditioning Anyone?

Rich_L

I was presented with an interesting question yesterday by one of my industrial customers. They are a large nitrogen user for part of the production process they do and they asked if there is such a thing as a nitrogen powered AC unit. They have bulk nitrogen stored in liquid form and it goes through a gasification process, basically a large evaporator outside, to boil it off to a gas. This evaporator stays very cold even in the hottest summer days. They are wondering if there may be a unit that we could pipe their nitrogen through that could take advantage of that huge energy transfer going on outside to supplement the large cooling load in their production area. They believe, and I agree, that if we could capture this it could be a great energy and cost savings to them. I LOVE the idea! Has anyone heard of such equipment or know where I could begin looking?



Thanks for any help you may be able to provide!

Rich L.

bruce_21

water to air heat pump

I don't know what sort of configuration the outside evaporator is but there should be a way to insert or wrap some tubing through or near enough to it that water or glycol pumped through the tubing would be cooled, then run through the heat pump to provide a heat sink. Again I don't know what sort of A/C they have, but if they have chilled water units you could go straight to them with the chilled water. Some thoughts. Do you have more details and pictures of what they have on both ends now?

landmobile

A few thoughts ...

First, is the nitrogen use constant throughout the day/week/year?   Second, does the use of nitrogen always coincide with the need for cooling in other areas of the building? 

 

If the nitrogen use in production and the cooling needs are more or less concurrent, the next question to ask is how much liquid nitrogen is used and how much energy does it take to evaporate it.  The latent heat of vaporization for nitrogen is 199 kiloJoules/kilogram and the specific heat is around 1 kiloJoule/kilogram-degree C.  If you know the quantity of liquid nitrogen used per hour, these numbers can give you a rough idea of how much theoretical cooling is available from the evaporation process.



The next step would be to compare the available cooling with the actual cooling load of the building and see if they are anywhere close to each other.  If they are, you would need to design a system to exchange heat from the building with the nitrogen evaporator.  I don't know enough about the specifics of such systems to comment (babble) further, but a few pitfalls come to mind:



The boiling point of nitrogen is -196 degrees C so the design would have to account for the possibility of very cold temperatures.

You would also need to provide for alternate means of nitrogen evaporation if the building's cooling needs vary seasonally.

Tom Blackwell_2

Cryogenic Vaporizer

Absolutely;  used a Cryogenic Vaporizer to produce 30 degree brine on a solvent recovery system some years ago.  The only problem is that the device is rather pricey.  It would normally be set up in series with the finned vaporizer as a 1st stage.  The vaporizer is set up internally such that the brine solution or chilled water will nor freeze during operation.  This is an excellent application if you use a large amount of nitrogen and have use for process or even comfort cooling chilled water.